Peel and finely chop the white onions.

Sauté the onions in a little olive oil until browned, then add the chopped garlic and sage leaves.

Season with salt, pepper, and a pinch of sugar. Deglaze with the balsamic vinegar.

Add the chicken stock and simmer gently for 1½ hours.

When cooked, pour the soup into individual ovenproof bowls (e.g., lion’s bowls).

Place the toasted bread slices on top of the soup, sprinkle generously with Grana Padano cheese, and gratinate under the oven grill for 10–12 minutes, until golden.

Sprinkle with chopped parsley before serving.